As a tape drive unit capable of writing data to a magnetic tape and reading data recorded on the magnetic tape, there is known a so-called tape streamer drive. The tape streamer drive is used in many applications such as back-up of data recorded on a recording medium such as a hard disc provided in a computer body or the like because a magnetic tape provided in a tape cassette has an extremely large recording capacity, that depends upon the length of the magnetic tape, such as tens to hundreds gigabytes. Also, the tape streamer drive is very suitable for storage of large-size data such as image data or the like.
For appropriate data recording to or reproduction from the magnetic tape in the tape cassette in a data storage system including the above-mentioned tape streamer drive and tape cassette, there are required various types of information on positions on the magnetic tape and a magnetic-tape use history are required as management information or the like for use by the tape streamer drive to manage the data recording and reproducing operations, etc.
To this end, an area for such management information is provided at the top of a magnetic tape or at the top of each of partitions formed on a magnetic tape. In the tape streamer drive, the area of the magnetic tape where management information is recorded is accessed and necessary management information is read from there before data is recorded to or reproduced from the magnetic tape, and operations are managed based on the management information for subsequent data recording or reproduction to be done appropriately.
After completion of the data recording or reproduction, the tape streamer drive accesses the management information area to rewrite the management information having to be changed due to the data recording or reproduction, the management information is thus rewritten for a next recording or reproduction. Thereafter, the tape cassette is unloaded or ejected from the tape streamer drive.
For data recording or reproduction to be done based on the management information as above, the tape streamer drive has to access the management information area at the top of the magnetic tape or each partition on the magnetic tape at the start of the data recording or reproduction to write or read the management data, and also access the management information area at the end of the data recording or reproduction to write or read the management information. That is, the tape cassette cannot be loaded or unloaded in any middle position on the magnetic tape where it is considered the data recording or reproduction has ended.
In the tape streamer drive, since the magnetic tape has to physically be fed for access to the management information area, access, made at the end of the data recording or reproduction, to the management information area at the top of the magnetic tape or at the top of each partition on the magnetic tape will take a long time. Especially, when the data recording or reproduction has ended in a rather far position on the magnetic tape from the management information area, the magnetic tape has to be fed over a correspondingly increased length and hence for an extra long time to access that area.
In the data storage system that uses a tape cassette as a recording medium, the time taken until one data recording or reproduction is complete, that is, a time after the management information area is accessed at the time of magnetic tape loading until that area is accessed again at the time of magnetic tape unloading, will be relatively long. The time required for such a series of access operations should desirably be as short as possible.
To this end, it has been proposed to provide a nonvolatile memory, for example, inside the tape cassette and store management information in the nonvolatile memory. In a tape streamer drive designed for use with such a tape cassette, an interface for data write to or read from the nonvolatile memory is provided to make it possible to read or write, from or to the nonvolatile memory, management information on the data recording to and reproduction from the magnetic tape. Thus, it is made unnecessary to rewind the magnetic tape to the tape top, for example, at each time of loading or unloading the tape cassette. That is, even with the magnetic tape being in a middle position, the tape cassette can be loaded or unloaded.
In the meantime, there is available a system compatible with the aforementioned tape cassette. It is a data storage system to back up data for a host computer. The data storage system normally includes a tape streamer drive capable of data recording to or reproducing from a tape cassette, and a host computer connected by a predetermined data interface to the tape streamer drive. For example, information stored in a hard disc of the host computer when recording it to the magnetic tape in the tape cassette is backed up according to a backup application software program started up in the host computer. Namely, according to the backup application software program, the host computer transfers the information stored in the hard disc to the tape streamer drive. Also, under the control of the host computer, the tape streamer drive drives the tape cassette loaded therein and writes the data transferred from the host computer's hard disc to the magnetic tape in the tape cassette according to the backup application software program. Thus, the information is backed up.
In this backup operation in the data storage system, by way of example, how to operate the tape cassette as a recording medium is all managed by a host system, namely, the host computer. In other words, the tape cassette itself cannot give the host system any designation of an intended operation corresponding to its own application or the like.
When the tape cassette is provided with a memory having management information stored therein, for example, the aforementioned data storage system can manage the data recording and reproduction by reading or writing the management information stored in the memory. Since the recording and playback based on the management information can be done on condition that a host system manages update of such management information or the like, the tape cassette is only operated according to the management information.
In the current data storage system in which the tape cassette is only operated according to a system operation, the tape cassette or tape streamer driver, subordinate to a host computer, for example, cannot control any system operation correspondingly to an intended use of the tape cassette and the like.
A system, using a tape cassette and constructed so that the tape cassette, tape streamer drive or the like can positively control the operation of a host system, will be more highly extensible and controllable.